A core was made of porous graphite to fit a preformed electrode. This porous-core electrode replaces old popular methods using graphite powder as an absorbent to accomplish concentration of liquid samples, but without causing contamination problems of Teflon® ware. When the amount of sample solution is not limited, a concentration of several thousand times is possible, to extend detection limits required by the modern electronics industry. High-purity water, solvents, volatile acids, and alkali were concentrated, and ultra trace impurities were determined. Some organic material can be ashed at 400°C on the electrode for arcing. Boron in trichlorosilane was separated with an addition of mannitol and routinely determined in low ppba range. The cost of this operation is a small fraction of that for new instrumentation required for achieving these sensitivities. The old spectrograph with a dc arc source unit and photographic detection has found some applications to meet new stringent requirements. The technique should be able to be easily applied to the determination of metallic impurities in trichlorosilane, dichlorosilane, hydrogen chloride, and others.
M. S. Wang, "Porous-Core Electrode for Emission Spectroscopy," Appl. Spectrosc. 42, 1090-1096 (1988)